Noise from ships interfere with the ability of endangered killer whales to 'talk' to each other and hunt, suggests a new study.

Researchers found underwater sound pollution along the coast of the Pacific disrupts how orca's communication with each other, and interferes with their ability to track and hunt salmon.

They said the 'unprecedented study of ship noise' will help biologist understand the potential effects it has on marine life, and help discover ways to reducing the interference.

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Researchers have found underwater sound pollution along the coast of the Pacific disrupts how orca's communication with each other, and interferes with their ability to track and hunt salmon. This noise pollution is caused by ships and boats travelling through the region (stock image)

Scientists set out to discover if noise from a nearby shipping lane interferes with the orca's ability to send out clicks and listen for their echoes in the ocean off Seattle while hunting salmon.

The researchers measured underwater noise as ships passed their study site 3,000 times.

They said the 'unprecedented characterisation of ship noise' will aid in the understanding of the potential effects on marine life, and help with ways of reducing the interference.

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Research has shown that the growth in commercial shipping has raised the intensity of low-frequency noise in the ocean almost 10-fold since the 1960s.

Because the noise occurs at similar low frequencies used by baleen whales there is growing evidence it may impact their ability to communicate, and therefore their survival.

To analyse the nature of ship noise, particularly in coastal areas close to ports, scientists measured around 1,600 unique ships as they travelled through Haro Strait, in Washington State (highlighted). This is a critical habitat for the endangered Southern Resident killer whales

Orcas, like other toothed whales, (stock image) use mid- and high-frequencies to communicate and find their prey so the study measured a wide range of frequencies from 10 Hz to 40,000 Hz. The results found ships are responsible for elevated levels at these frequencies - including at 20,000 Hz where killer whales hear best

HOW NOISE IMPACTS WHALES

Research has shown commercial shipping has raised the intensity of low-frequency noise in the ocean 10-fold since the 1960s.

As the noise occurs at similar low frequencies used by baleen whales there is evidence it impacts their ability to communicate.

Because the orcas, like other toothed whales, use mid- and high-frequencies to communicate and find their prey, the study measured a wide range of frequencies (10 Hz to 40,000 Hz).

The results showed ships are responsible for elevated background noise levels not only at low frequencies as expected, but also at medium and higher frequencies - including at 20,000 Hz where killer whales hear best.

But the team behind the new research wanted to know if ship noise could extend to the higher frequencies used by toothed whales and therefore pose similar threats to them.

To analyse the nature of ship noise, particularly in coastal areas close to ports, scientists measured around 1,600 unique ships as they travelled through Haro Strait, in Washington State.

This is a critical habitat for the endangered Southern Resident killer whales.

The orcas are iconic in the Pacific Northwest and support a multi-million dollar ecotourism industry in the United States and Canada.

Because the orcas, like other toothed whales, use mid- and high-frequencies to communicate and find their prey, the study measured a wide range of frequencies (10 Hz to 40,000 Hz).

Study author Doctor Scott Veirs, of Beam Reach Marine Science and Sustainability School, said: 'The results show that ships are responsible for elevated background noise levels not only at low frequencies as expected, but also at medium and higher frequencies - including at 20,000 Hz where killer whales hear best.

'Overall, container ships exhibited the highest median source levels at all frequencies below 20,000 Hz. Whales travel in pods and use a range of noises to 'talk' to each other and send messages around the group. These include clicks, whistles, and calls (stock image)

HOW WHALES 'TALK' TO OTHERS

Whales travel in pods and use a range of noises to 'talk' to each other and send messages around the group.

These include clicks, whistles, and calls.

Clicks are thought to be used for navigation, similar to how bats use sonar, and when sound waves hit objects, the whales can identify them.

Meanwhile, whistles and calls are for socialising.

These calls and whistles are made at different frequencies, but are typically in the range of 20,000 Hz for killer whales.

Marine biologists have also noticed that the sounds made by different pods have different 'accents', this is likely to help whales identify whales within its own pod.

'This means that in coastal environments where marine mammals live within a few kilometres of shipping lanes, ship noise has the potential to interfere with both communication and echo-location.'

He added: 'The study is unique because it estimates the source levels of larger populations and more classes of ships than in previous studies.